In poor communities, people often have to shop for food, and other necessities at stores owned by people outside the neighborhood.

In poor communities, people often have to shop for food and other necessities at stores owned by people outside the neighborhood.

The comma after the introductory phrase is correct in both sentences. But no comma is needed before and because it does not join two independent clauses. So the second sentence is correct.

For more help, see section P1.